No experience with the Computrainer but seems to me that 'time' has to be thrown into the mix as well. I think the aim is to run a set of brief time trials on the trainer using the same gearing and attempting to maintain the cadence over a set time interval to measure increase/decrease in time that power output can be maintained versus previous setups - heart rate would also seem a useful number as it would be a good inidcator of the bodies workload at the dictated power level. One thing I do know is that all of this effort will be wasted unless you first 'diagram' the bikes baseline setup in order to have a baseline from which to start as well as to use later to reproduce position should oyu switch equipment.

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¯\_(ツ)_/¯

Last winter I spent ~2 weeks optimizing my position on the bike using my CT. A few key observations:
- exactly record your bike set-up, and pick a TT course. Ride it and record HR, PWR, RPM, RPE.
- vary exactly 1 parameter in your bike setup, i.e. seat height, seat for-aft positioning, but not by a large amount, i.e. 1-2 cm at a time.
- re-ride the TT course at same level of effort/RPE, recording same parameters.

What I found is that the biggest issue is patience. I.e. Riding the same TT more than once in a given session at race pace will likely result in inaccurate measurements the second or later time around. So I ended up making 1 change in setup per day, do a TT ride, record everything in a spreadsheet, and then resort to analysis.

Re. TT length: I found that anything less than 10 miles could lead to 'false positives', i.e. a given bike set-up might feel good, but when taking the bike out on a longer weekend ride it would turn out to be uncomfortable.

Over time you will see trends emerge, i.e. stretching yourself out to become more aero will steal watts at same RPE, etc. Using the trends you should then take the 'best' position out on the open road for a longer ride, as the best CT session does not make for controlling a rolling bike, winds, etc. Combine a road ride on a given set-up with a transition run, to ensure that you don't just have a good TT set-up, but a good tri set-up, i.e. don't have a great bike split at the expense of shuffling the run.

In addition, I read whatever I could get my hands on wrt bike set-up (Dan's excellent article is a great starting point) which gives angles. Record yourself on film, freeze the frame, measure your angles. There's a very high probability that whatever you come up with for optimal position will be very close to commonly accepted fit standards.

Bottomline is that your set-up needs to feel good. Your body is the best judge. Listen to it.

Thanks for the advice.

What made me suspect my tri bike setup isn't optimal is I bought a new road bike and set it up. When I put it on the trainer I seemed to have a lot more power at the same PE than when on the tri bike.

Since then I took the road bike out on a 75 K loop I frequently do. My observations so far are that the road bike is better handling and seems to accelerate better but the tri bike is easier to sustain power on (probably due to being more aero). I'll play around on the Computrainer over the winter and see what I can learn about setup of both bikes.

I have all measurements logged for my bikes and will graph the effect of small changes. Worst case is no improvement and I'll switch back to the proven setup.

Everything you say makes total sense.

More power on road bike: road bikes have a shallower seat angle, allowing you to use most notably the quadriceps (largest muscle group in your body) a lot more than on a steeper-angled (i.e. tri) bike. At the same RPE you'll be able to generate more power. However, you generate them with different muscles, and as a result won't be as fresh or lasting on a run when coming off the road bike.

Better handling road bike: different seat angle distributes the weight differently on the bike, i.e. more weight is on the rear wheel when compared to a steeper seat angle.

Better acceleration on road bike: see above on more involvement of quads in power generation on road geometry/seat angle.

Have fun playing with your set-up on the CT. It's quite educational, and will help you understand bike positioning as it pertains to your personal need, which is invaluable.

- S

The Computrainer is an excellent fit tool if you are only fitting for use on a Computrainer.

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Tom Demerly
The Tri Shop.com

Tom - see spd above. one needs to check the set up on the road before making a final determination. a CT will show you what a drop will do to your watts, which may or may not be useful on the road.

Tom,

So, is it a waste of time doing things like seeing how low the front end can go before losing power, etc. on a Computrainer?

I had my Saber fit by a FIST certified bike fitter and find it quite comfortable. I was just wondering if tweeking the fit could make any difference.

Brent, don't listen to Tom on this one. maybe he'll return to clarify his post. i think it is a good idea to use a CT to monitor your drop vs. wattage. bearing in mind, though, i don't FIT nor FIST like Tom. but, it makes sense to drop to get more aero, but not so much so that you lose watts.

Well, I think this might exactly be one of the shortcomings that Tom referred to in his last statement. Wattage for wattage sake does not win you a race. I.e. do a max power test on a road bike vs a tri bike. Assuming 'proper' tri and road set-up, you'll see higher wattage on the road bike.
Moving the saddle forward (i.e. steepening the seat angle) will lose you wattage as well, but allow you to place yourself more aerodynamically on the bike, and save some muscles for the run.
Where the art and fit specialists come in (well, one of many reasons .... :) is to help determine the best possible compromise between comfort, aerodynamic positioning and power output for your personal needs and constraints. Working with a good fitter will save you many hours and quite possibly $ (for trying different stems/seat posts/aero bars etc etc).
Doing it yourself just on a compuTrainer can easily lead to maximizing one of the three parameters (power, comfort, aero) at the cost of one or both others. The trick is finding the perfect balance.

   

This goes back to the inertial loading issue that was recently addressed in another thread. You use your muscles differently on a trainer than you do on the road. So it's not the best place to optimize your position.

It used to be that after riding on the CT for weeks, I'd get sore the first time I'd go out on the road. Since I put a huge freakin 18lb flywheel on the CT, it's a little better. But, muscle recruitment is still different.



-- Jens